Solid state conduction circuit used as a television receiver display device



3,363,056 EVISION SOURCE REFRIGERATION W. C. DUNLAP. JR

RECEIVER DISPLAY DEVICE Original Ffiled Sept. 24, 1959 SOLID STATECONDUCTION CIRCUIT USED AS A TEL VOLTAGE SOURCE Jan. 9, 1958 SYNC.VOLTAGE SOURCE INVENTOR WILLIAM C. DUNLAP JR.

ATTORNEY SOURCE LIGHT VOLTAGE SOURCE REFRIGERATION SOURCE VOLTAGE SOURCEUnited States Patent 3,363,056 SOLID STATE CONDUCTION CIRCUIT USED AS ATELEVISION RECEIVER DISPLAY DEVKCE William C. Dunlap, J12, Cambridge,Mass, assignor to The Bendix Corporation, Sonthfield, Mich, acorporation of Delaware Original application Sept. 24, 1959, Ser. No.842,009. Divided and this application Oct. 7, 1964, Ser. No. 402,264

7 Claims. (Cl. 178-13) ABSTRACT OF THE DISCLOSURE A television receivingtube constructed of a body of high-purity semiconductor material atcryogenic temperature having a source of modulated carriers connected atone end of the body, a fluorescent coating at the opposite end of thebody, accelerating grids for accelerating the modulated carriers throughthe body to the fluorescent coating, and horizontal and verticaldeflectors to sweep the carriers.

This invention pertains to a semiconductor device and more particularlyto a device for providing direct carrier motion instead of drift motion.This is a division of my copending application Ser. No. 842,009, filedSept. 24, 1959, now US Patent 3,176,146, entitled, Semiconductor SwitchUtilizing Low Temperature and Low Impurity Content.

In prior semiconductor devices, motion of the carriers in the device wasrestricted to diffusion or drift wherein the carriers were constantlyundergoing a change in direction due to frequent interferences withlattice vibrations and collisions with semiconductor impurities. Forthese reasons the mobilities and mean free path of the carriers wereminute and, therefore, a beam of electrons could not be established andfrequency response was limited.

This invention provides for increasing the mobilities and mean free pathof carriers in semiconductor devices preferably to a length of the orderof the distance between electrodes, spaced a working distance apart, sothat semiconductors may be used in applications previously restricted tovacuum tubes. Increased mobility makes possible high frequencyapplications such as switches. In addition, since the effective mass ofcarriers in semiconductor materials are believed to be but a fraction ofthe masses in a vacuum tube, acceleration and other carrier velocitychanges may be accomplished in a much shorter distance therebydecreasing component size and further increasing the maximum frequencypossible in a switching mechanism.

This invention provides these advantages by reducing the semiconductortemperature sufliciently to decrease lattice vibration and by increasingthe purity of the semiconductor material so that interference tocarriers will be minimized. Selection of materials having normally lowlattice vibration will reduce the need for the low temperaturerequirements.

It is, therefore, an object of this invention to provide a semiconductordevice having increased carrier mobility and mean free path length.

It is another object to provide a semiconductor device wherein thetemperature is reduced to reduce lattice vibrations and wherein thepurity is increased to reduce interference to carrier travel.

It is another object to provide a television receiving tube comprising abody of semiconductor material at a low temperature and of increasedpurity with means for supplying a beam of energy entering one portion ofthe semiconductor body, a modulating grid for modulatice ing the energyof the beam in proportion to the picture information received from atelevision camera, accelerating grids for accelerating the modulatedenergy source, means for deflecting the accelerated energy beam in bothhorizontal and vertical directions to obtain a beam sweep, a fluorescentcoating on a portion of the body which is swept by the energy beam andilluminates in proportion to the instantaneous strength of the energybeam, and a light amplifier and screen for enlarging the picture on thefluorescent surface.

These and other objects will become more apparent when detaileddescriptions of several preferred embodiments are considered inconnection with the drawings, in which:

FIGURE 1 is a schematic View of a high frequency switch incorporatingthe semiconductor device of this invention; and

FIGURE 2 is a schematic, partially perspective view of a televisionreceiving tube incorporating a semiconductor device of this invention.

In FIGURE 1 is shown a switching device comprising a germanium wafer 20having an input electrode 22 connected at one end thereof for receivingenergy and a pair of output electrodes 24, 26. The wafer 20 is highlypurified so as to reduce interference of the carriers established by theinput energy from electrode 22. The purification may be in the order ofIO --10 impurity atoms per cubic centimeter of material. Thepurification required depends on the desired mean free path, thematerials used and the temperature of the semiconductor.

The wafer 20 is also encased in an enclosure 28 which is connected to arefrigerator 30 for maintaining the temperature of the wafer at very lowlevels, such as 5 Kelvin, for germanium. At this temperature the latticevibrations of the germanium wafer are reduced sufliciently so thatenergy entering at electrode 22 will form intrinsic carriers in thewafer which, owing to the lack of interference, can pass directly toeither output 24 or 26. In order to control the output to which thecarriers will go, an electric field is placed across the wafer. Meansfor doing this include a pair of deflection plates 32 which areconnected to a voltage source 34. With the plates 32 at one voltage, thebeam of carriers through wafer 20 will be directed to output 24 alongpath 36 and with the voltage on plates 32 being at another level, thecarriers will be directed toward output 26 along path 38. Very highswitching frequencies are obtainable with this device since theeffective mass of the carriers in the germanium can be as small as ofthe masses of electrons in a vacuum tube.

A further embodiment is shown in FIGURE 2 which may be used as atelevision receiving tube. A source 40 emits a light beam 42 whichstrikes a phosphor coating 44 on the face of a germanium cube 46 whichis of very high purity. Germanium cube 46 is enclosed by casing 48 theinterior of which is maintained at a very low temperature such as 5Kelvin by refrigerating means 59. A grid 52 is placed in the cube 46adjacent the coating 44 and has a modulating voltage supplied theretofrom receiver 54. Variations in the voltage of receiver 54 will controlthe number of intrinsic carriers generated as light beam 42 impinges onphotoemissive coating 44.

Connected to the opposite face of cube 46 is an accelerating grid 56which is supplied with a high potential from a source 58 foraccelerating the electrons established in cube 46. Since the etfectivemass of an electron in a semiconductor material is as low as of the massof an electron in a vacuum tube, the required accelerating length iscorrespondingly reduced. Coated on the opposite face of cube 46 is afluorescent coating 60 which may be of phosphor or other suitablematerial. When the accelerated beam strikes the layer 60, a light ofcorresponding intensity is emitted.

Deflecting plates 62, 64 are placed on opposite sides of cube 46 andreceive a high frequency, synchronized voltage from source 66 to imparta horizontal sweep to the electron beam formed by the impingement oflight ray 42 on coating 44. Plate 68, 70 are placed above and below cube46 and receive a high frequency, synchronized voltage from source 72 toimpart a varying vertical field to the electron beam. The frequencies ofthe voltages applied to plates 62, 64 and 68, 70 are such as to providea sweeping action of electron beam along the coating 60 often enough topresent a continuous picture to the eye in the maner known to the art.The picture presented on coating 60 is amplified and projected on ascreen 72 to desired dimensions by conventional means.

Although this invention has been disclosed and illustrated withreference to particular applications, the principles involved aresusceptible to numerous other applications which will be apparent topersons skilled in the art. The invention is, therefore, to be limitedonly as indicated by the scope of the appended claims.

Having thus described my invention, I claim:

1. A solid state conduction apparatus comprising a body of semiconductormaterial having inherent lattice vibrations,

means to control the temperature of said body to regulate saidvibrations,

means to establish carriers in said body,

said body having a predetermined purity to minimize interference to saidcarriers,

means for emitting a radiation source beam,

a photoemissive coating being on said body for receiving said beam,

at first voltage controlled grid means being in a plane adjacent saidcoating to control particle emission from said coating,

a second voltage controlled grid means spaced from said first grid meansto accelerate the emitted particles in said body,

a fluoroescent coating being on said body to receive said acceleratedparticles from said body.

2. A solid state conduction apparatus comprising a body of semiconductormaterial having inherent lattice vibrations,

means to control the temperature of said body to regulate saidvibrations,

means to establish carriers in said body,

said body having a predetermined purity to minimize interference to saidcarriers,

means for emitting a radiation source beam,

a photoemissive coating being on said body for receiving said beam,

a first voltage controlled grid being in a plane adjacent said coatingto control particle emission from said coating into said body,

voltage controlled deflection plates being located adjacent said body tocontrol the direction of said emitted particles in said body,

a second voltage controlled grid spaced from said first grid toaccelerate the emitted particles in said body,

a fluorescent coating being on said body to receive said acceleratedparticles from said body,

said deflection plates including a first pair of substantially parallelplates,

and a second pair of substantially parallel plates aligned substantiallyperpendicular to said first pair of plates,

means to control the voltage on said plates so as to cause theaccelerated radiation source beam to sweep said fluorescent surface.

3. A solid state conduction apparatus comprising a body of semiconductormaterial having inherent lattice vibrations,

means to control the temperature of said body to regulate saidvibrations,

means to establish carriers in said body,

said body having a predetermined purity to minimize interference to saidcarriers,

means for emitting a radiation source beam,

a photoemissive coating being on said body for receiving said beam,

a first voltage controlled grid being in a plane adjacent said coatingto control particle emission from said coating into said body,

a second voltage controlled grid spaced from said first grid toaccelerate the emitted particles in said body,

a fluorescent coating being on said body to receive said acceleratedparticles and thereby to form a light image,

a screen of a preselected size being aligned to receive the light imagefrom said fluorescent coating.

4. A solid state conduction apparatus comprising a body of semiconductormaterial having inherent lattice vibrations,

means to control the temperature of said body to regulate saidvibrations,

means to establish carriers in said body,

said body having a predetermined purity to minimize interference to saidcarriers,

means for emitting a radiation source beam,

photoemissive means being adjacent said body for receiving said beam,

first means being in a plane adjacent said photoemissive means tocontrol particle emission from said photoemissive means,

deflection means being located adjacent said body to control thedirection of said emitted particles in said body,

second means spaced from said first mens to accelerate the emittedparticles in said body,

fluorescent means being adjacent said body to receive said acceleratedparticles from said body.

5. A solid state conduction apparatus comprising a body of semiconductormaterial having inherent lattice vibrations,

means to lower the temperature of said body to a temperature of 20Kelvin or less to reduce said-vibrations thereby providing a relativelyfree path for carrier flow through the semiconductor body,

said body having an impurity content of 10 impurity particles per cubiccentimeter or less,

means for emitting a radiaton source beam,

photoemissive means being adjacent said body for receiving said beam,

grid means being in a plane adjacent said photoemissive means to controlparticle emission from said photoemissive means,

deflection means being located adjacent said body to control thedirection of said emitted particles in said body,

second grid means spaced from said first grid means to accelerate theemitted particles in said body,

fluorescent means being adjacent said body to receive said acceleratedparticles from said body.

6. A solid state conduction apparatus comprising a body of semiconductormaterial having inherent lattice vibrations,

carrier source means,

means to lower the temperature of said body to a temperature of 20Kelvin or less to reduce said vibrations thereby providing a relativelyfree path for carrier flow through the semiconductor body,

said body having an impurity content of 10 impurity particles per cubiccentimeter or less,

screen means locally responsive to impact of said carriers being on onesurface of said body for providing an output which is indicative ofpoint of impact of said carriers,

means to sweep said screen means with said carriers.

7. A solid state conduction apparatus comprising a body of semiconductormaterial having inherent lattice vibrations,

means to lower the temperature of said body to a temperature of 20Kelvin or less to reduce said vibrations thereby providing a relativelyfree path for carrier flow through the semiconductor body,

said body having an impurity content of 10 impurity particles per cubiccentimeter or less,

means for emitting a radiation source beam,

a photoemissive coating being on said body for receiving said beam,

a first voltage controlled grid means being in a plane adjacent saidcoating to control particle emission from said coating,

a second voltage controlled grid means spaced from said first grid meansto accelerate the emitted particles in said body,

a fluorescent coating being on said body to receive said acceleratedparticles from said body,

6 voltage controlled deflection plates being located adjacent said bodyto control the direction of said emitted particles in said body, saiddeflection plates including a first pair of substantially parallelplates, and a second pair of substantially parallel plates alignedsubstantially perpendicular to said first pair of plates, means tocontrol the voltage on said plates so as to cause the acceleratedradiation source beam to sweep said fluorescent surface.

References Cited UNITED STATES PATENTS 2,944,167 7/1960 Matare 30788.53,176,146 3/1965 Dunlap 30-788.5

JOHN W. CALDWELL, Primary Examiner.

J. A. ORSINO, Assistant Examiner.

